The simplification of paper feeds is a goal in the design of any typewriter or printer, so long as they may be simplified without reducing reliability in feeding the paper. In an effort to simplify paper feed, a self-aligning and non-adjustable paper feed mechanism is of primary interest. The self-alignment eliminates the need for precise positioning of the paper feed assembly while non-adjustable paper feeds eliminate the expense of manufacturing the adjustment capacity into the paper feed and the expense of performing the adjustments. Simple release controls eliminate assembly problems and thereby tend to reduce manufacturing and assembly costs. The need for a simpler mechanism is dictated by costs and reliability together with the need to automate the assembly of apparatus such as typewriters and printers to be cost effective in the marketplace.
A self-aligning paper feed for a typewriter is disclosed in U.S. Pat. No. 4,364,683 to I. D. Shakib et al. The release of the paper feed disclosed in the Shakib et al patent depends upon the release bail engaging a release surface and pulling the feed roll assembly away from the platen to allow insertion of the paper or movement of the paper with respect to the platen.
The paper feed of the Epson MX80F/T printer is one where a bail has coaxially mounted thereon a pair of feed rolls spaced apart slightly and positioned roughly at the mid point of the bail. The bail is pulled by a spring into a slot in the frame and maintained in that position by a spring. The end of the slot acts as a fulcrum for the bail while the opposite end of the bail is engaged by a control lever and can be forced generally radially outward from the platen axis. With the movement outward, the feed rolls, being mounted at approximately the midpoint of the bail, will then move outward, also in a generally radial direction from the axis of the platen by approximately half the distance the free end of the bail is translated. One disadvantage of this type paper feed is that the feed rolls will have a tendency to exert an uneven force on the platen depending upon the thickness of the paper being fed and particularly when multiple-part forms are being fed. A further disadvantage of this system is that there is no self-aligning capability.